The invention relates to fuel injection for diesel engines and, more particularly, to the high-pressure lube-oil supply system therefor.
FIGS. 1 and 2 show a conventional fuel injection system 20 for a diesel engine and high-pressure lube-oil supply system 30 as well, all in accordance with the prior art. For sake of an example, FIG. 1 is a schematic based upon a model T444E diesel engine of the Navistar International Transportation Corporation (circa 1994).
In general, the fuel system 20 has a pump 22 drawing fuel from a tank 24 and pumping it through a filter 26. Fuel pumped from this stage is divided through steel lines that lead into the back of each cylinder head. Each of these lines supplies a stream of fuel to a respective gallery drilled in each respective head, wherein these galleries intersect each injector bore to the cylinders. The fuel system 20 utilizes hydraulically-actuated injectors 28 to inject fuel into each cylinder. The hydraulic fluid utilized for this service is the engine's lube oil. Accordingly, to handle such a service, there is naturally some fashion of a pressurized lube-oil system (i.e., indicated as 30). Indeed, it is more conventionally referred to as a high-pressure lube-oil system 30 or the like.
The high-pressure lube-oil system 30 is able to produce operating pressures in a range between about 500 and 3000 psi (3,500 and 20,000 kPa) for service of hydraulic actuation of the fuel injectors 28. The fuel injectors 28, although driven by the actuation pressures noted just previously, are arranged to amplify/boost the delivered drive-pressures of the lube-oil such that the injected fuel (e.g., injected into the combustion chambers, but ejected from the injectors 28) is pressurized all the way up to about 18,000 psi (125,000 kPa).
As FIG. 1 shows better, the high-pressure lube-oil system 30 draws lube oil from the oil pan 31 through a pickup tube by an engine oil (i.e., lube oil) pump. The engine oil pump can be a gerotor type pump mounted-axially on the front end of the crankshaft, which drives it. Lube oil is pumped through an oil cooler 33, then oil filter 35, and conducted through passages in the crankcase's front cover to the high-pressure lube-oil system 30's reservoir that is mounted on top of the crankcase's front cover (the reservoir is not depicted in this drawing, but is indicated as 44 in FIG. 2).
The reservoir 44 makes available a constant supply of lube oil to a high-pressure lube-oil pump 32, which is mounted to a neck portion of the crankcase's front cover, and from there extends back into the engine block's “V.” Preferably the high-pressure lube-oil pump 32 is a nine (9) plunger swash-plate pump that has a drive gear that is driven by a camshaft gear. High pressure lube oil is divided between a left and right supply line for the LH (left cylinder head) and RH (right cylinder head) oil-galleries. Each oil gallery supplies the high pressure lube oil to a series of branching oil rails. The oil galleries and oil rails are all machined into the cylinder heads.
In operation, when an injector 28 is energized, a poppet valve thereof is opened by an attached solenoid valve (these are not shown). Pressurized lube oil is allowed to flow into the injector 28 and drive against an amplifier piston (not shown). When injection is ended, the lube oil pressure which was just previously applied to the amplifier piston is successively then vented by the poppet valve, and onward through oil spouts mounted on the top of the injector 28, which not only releases the pressure applied to the amplifier piston but also returns the spouting lube oil to the sump 31.
Control over the lube oil's service pressure is obtained by means of, in combination, data signals provided by an injection control pressure (ICP) sensor (not shown), and injector drive module (IDM) 37, control instructions sent by electronic control module (ECM) 39, which are acted upon by an injection pressure regulator (IPR) valve 34. By way of background, the high-pressure lube-oil pump 32 is designed to deliver output at simply one design pressure. Regulated control over the lube oil's service pressure is henceforth obtained by the injection pressure regulator (IPR) valve 34, which is mounted in a cavity for it in the body of the high-pressure lube-oil pump 32. The IPR 34 regulates service pressure by dumping excess lube oil through a check valve into the crankcase's front cover, eventually to drain back down to the sump 31.
There are various shortcomings with the prior art high-pressure lube-oil system 30. As a matter of background, if a mechanic wishes to optimize a diesel engine for performance, one choice involves exchanging the original factory-equipment injectors for larger, custom or high-performance injectors.
Alternatively or in addition, the controller 39's control over the injectors 28 might be changed to dwell longer. Either way, bigger injectors or longer dwell means a greater rate of fuel consumption. But the problem is this. That is, there isn't a sufficient supply of high-pressure lube oil to keep pace with such greater rate of fuel consumption. Typically, the original-equipment high-pressure lube-oil pump 32 is simply under-capacity to meet the increased capacity needs.
What is needed is a solution which overcomes the shortcomings of the prior art.
A number of additional features and objects will be apparent in connection with the following discussion of preferred embodiments and examples.